The present invention relates generally to ladders. More particularly, the present invention relates to ladders having a plurality of slidable, nesting rung units.
The maintenance tasks which arise in homes, apartments, farms, factories and other places frequently call for the use of a ladder. When the ladder is not being used it must be stored someplace. While a longer ladder allows a person to reach more places, it may also be more awkward to handle and may take up more space when it is stored. An extending ladder can be placed in an extended state while it is being used and can be placed in a collapsed state while it is being stored. It would be desirable to provide a ladder having a collapsed state in which the ladder can be stored in a closet, under a bed, or in a car trunk.
Extending ladders and associated manufacturing methods are disclosed. A ladder in accordance with an exemplary embodiment of the present invention comprises a plurality of rung units, each rung unit including a left column, a right column, and a rung extending between the left column and the right column. The left columns are disposed in a nested arrangement for relative lengthwise movement in a telescopic fashion. Likewise, the right columns are also disposed in a nested arrangement for relative lengthwise movement in a telescopic fashion. In one aspect of a ladder in accordance with an exemplary embodiment of the present invention, a strap is disposed around the rungs for selectively precluding relative movement between the rung units.
A ladder in accordance with an exemplary embodiment of the present invention includes a first column assembly and a second column assembly disposed in a nested arrangement for relative lengthwise movement in a telescopic fashion. The first column assembly includes a first column and a ring that is coupled to the first column proximate a distal end thereof. The second column assembly includes a second column and a sleeve that is coupled to the second column proximate a proximal end thereof.
A portion of the second column assembly is disposed within a lumen defined by an internal surface of the first column so that an external guiding surface of the sleeve contacts the internal surface of the first column. An internal guiding surface of the ring contacts an exterior surface of the second column. In certain advantageous implementations, the first column assembly and the second column assembly contact one another only where the internal guiding surface contacts the exterior surface of the second column and where the external guiding surface contacts the internal surface of the first column.
In some implementations, the first column comprises a first material and the sleeve comprises a second material different from the first material. In certain advantageous implementations, the first material and the second material are selected so that galling is unlikely to occur when the first column and the sleeve are placed in sliding contact with one another. Also in certain advantageous implementations, the first material and the second material are selected so that a relatively low friction interface is provided when the first column and the sleeve are placed in sliding contact with one another. In some cases, the first material comprises aluminum and the second material comprises a polymeric material.
In some implementations, the second column comprises a first material and the ring comprises a second material different from the first material. In certain advantageous implementations, the first material and the second material are selected so that galling is unlikely to occur when the second column and the ring are placed in sliding contact with one another. Also in certain advantageous implementations, the first material and the second material are selected so that a relatively low friction interface is provided when the second column and the ring are placed in sliding contact with one another. In some cases, the first material comprises aluminum and the second material comprises a polymeric material.
In one aspect of a ladder in accordance with an exemplary embodiment of the present invention, the sleeve includes a landing surface and the first column includes a stop. When this is the case, the landing surface of the sleeve may advantageously contact the stop when a desired level of extension between the first column and the second column has been reached. In certain implementations, the stop comprises an inward projection. The inward projection may comprise, for example, a portion of a wall of the first column which has been displaced inwardly.
In an additional aspect of a ladder in accordance with an exemplary embodiment of the present invention, a ferrule is interposed between the external surface of the first column and an annular wall of the connector. In some advantageous implementations, the ferrule and the first column are fixed to one another at an interference fit joint formed between the ferrule and the first column. Also in some advantageous implementations, the ferrule and the connector are fixed to one another at an interlocking connection. In some cases, for example, the mechanically interlocking connection may comprise at least one protrusion of the ferrule which is received by a hole of the connector.
In another aspect of a ladder in accordance with an exemplary embodiment of the present invention, the sleeve is coupled to the second column at a mechanically interlocking connection. In certain implementations, the sleeve includes a plurality of protuberances which are received within openings defined by the second column for fixing the sleeve to the second column.
In still another aspect of a ladder in accordance with the present invention, the ladder may include a latch mechanism for selectively locking the second column relative the first column. In some cases, a button is operatively coupled to the latch mechanism for actuating the latch mechanism. In certain advantageous implementations, the button includes a depression which is dimensioned to receive a tip portion of the thumb of a ladder users hand. In certain particularly advantageous implementations, the button is shaped and positioned so that a depression of the button receives the tip portion of the thumb while the first column is grasped between a palm of the hand and at least one finger of the hand.
In yet another aspect of a ladder in accordance with an exemplary embodiment of the present invention, the ladder may include a plurality of collars. Each collar may be disposed about a column of the ladder. In certain advantageous implementations of the present invention, each collar is dimensioned so that a first connector will contact a first landing surface of the collar and a second connector will contact a second landing surface of the collar when the ladder is placed in a collapsed state.
Implementations of the present invention are possible in which the ring is coupled to the first column in a manner which allows the ring to float relative to the first column. In certain implementations, the ring is coupled to the first column by a connector which retains the ring in axial and radial directions relative to the first column while, at the same time, permitting some relative motion between the first column and the ring. When this is the case, the relative motion provided between the first column and the ring may advantageously have a magnitude which is sufficient to allow the ring to assume a position in which an internal guiding surface of the ring is disposed in coaxial alignment with the external guiding surface of the sleeve.
A method for assembling a ladder in accordance with the present invention may comprise the steps of 1) providing a connector having an annular wall defining a socket and a hole communicating with the socket; 2) inserting a ring into the socket of the connector; 3)inserting a ferrule into the socket of the connector; 4) locking the ferrule relative to the connector; and 5) inserting a column into a receptacle defined by the ferrule. In some advantageous methods, an interference fit joint is formed when the column is inserted into the receptacle defined by the ferrule. Also in some advantageous methods, the step of locking the ferrule relative to the connector comprises directing at least one protrusion of the ferrule into a hole of the connector.